This invention relates to a magnetic recording medium, typically a magnetic disk, and a writing/reading method therefor.
Computer magnetic disk units are under rapid development toward a greater capacity. The magnetic disk unit has a magnetic head which produces a signal magnetic field across the magnetic disk to form a row of recording magnetic domains in the recording layer. For increasing the areal recording density of the magnetic disk, it is crucial to miniaturize recording magnetic domains.
In prior art magnetic disks, most magnetic materials of which the recording layer is constructed are Coxe2x80x94Crxe2x80x94Ta and Coxe2x80x94Crxe2x80x94Pt systems. The inclusion of an additive element such as Cr, Ta or Pt along grain boundaries weakens the interaction between crystal grains and restrains the generation of a complex magnetic wall structure at the boundary of recorded bits, thereby improving the coercivity and squareness of the recording layer.
However, since the areal recording density of magnetic disk unit is now increasing at an annual rate of about 100%, a continuous improvement in recording density will lead to single recording bits of an extremely small size, at which fringing between adjacent recording bits becomes a problem. The term xe2x80x9cfringingxe2x80x9d means magnetic bleeding from the perimeter of recording magnetic domains caused by a magnetic field spatially diverging from a magnetic head.
One recording system for solving the problem associated with the increased areal recording density is a patterned medium as disclosed, for example, in JP-B 6-28039. The patterned medium has a structure that a recording layer is divided in a mesh pattern to isolate islands of magnetic material. The space between adjacent islands of magnetic material is filled with a nonmagnetic material.
The patterned medium allows the bit density and track density to be increased. However, as the track density increases, the alignment of the head becomes difficult. The patterned medium is difficult to control the write timing since a recording magnetic field must be applied in accordance with the position of minute magnetic material islands constituting minimum magnetic reversal units.
An object of the invention is to provide a patterned medium comprising recording tracks having minimum magnetic reversal units arranged with a nonmagnetic region intervening therebetween, which facilitates the alignment of a head and the control of write timing.
According to the invention, there is provided a magnetic recording medium in which minimum magnetic reversal units with a nonmagnetic region intervening therebetween are arranged in a two-dimensional pattern to form substantially parallel recording tracks. A plurality of minimum magnetic reversal units are arranged at equal intervals in longitudinal and transverse directions of the recording tracks to construct a cluster. The clusters are arranged at equal intervals in the longitudinal and transverse directions of the recording tracks. Each cluster has the same number of minimum magnetic reversal units arranged in the recording track longitudinal direction and the same number of minimum magnetic reversal units arranged in the recording track transverse direction. The center-to-center distance between two adjacent minimum magnetic reversal units in the recording track longitudinal direction is UL within the cluster and CL between adjacent clusters, satisfying CL/UL greater than 1. The center-to-center distance between two adjacent minimum magnetic reversal units in the recording track transverse direction is UW within the cluster and CW between adjacent clusters, satisfying CW/UW greater than 1.
In one preferred embodiment, the minimum magnetic reversal units are constructed of a perpendicular magnetizable recording material.
In another aspect, the invention provides a method for writing and reading signals of information in and from the magnetic recording medium defined above, comprising the steps of simultaneously writing signals of information in the minimum magnetic reversal units arranged in the recording track transverse direction within one cluster, and simultaneously reading the signals in the units.
Preferably, a write/read head comprising write elements and read elements is used, the number of write elements is equal to the number CN of minimum magnetic reversal units arranged in the recording track transverse direction within one cluster, and the number of read elements is greater than CN. Also preferably, a write/read head comprising write elements and read elements which are spaced apart in the recording track longitudinal direction is used, the timing to start writing in a cluster in which signals are to be written is controlled on the basis of the leading or trailing end of another cluster detected by the read elements.